Externally-reenforced construction and method of making the same



SPt 20511927; l J. H. LEVERING I 15643375 EXTERNALLY REENFORCED CONSTRUCTIONAND METHOD OF MAKING .THE SAME- Filed June 7, 1919*I f 6 Sheets-Sheet l ffm Ny/7H 'wirnes "12' y l A @Mg/W J. H. LEVERING Sept. 20, 1927.l

QF MAKING THE S'AME:

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J. H. LEVERING EXTERNALLY REENFORCED CONSTRUCTION AND METHOD OF MAKING THE SAME Filed June '7, 1919 6 Sheets-Sheet 3 Fly. 9.

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Patented Sept. 20, 1927.

UNITED STATES JAMES HENRY LEVERING, OF LOS ANGELES, CALIFORNIA.

EXTEBNALLY-REENFORCED CONSTRUCTION AND METHOD OF MAKING- THE SAME.

.application mea :une 7, 1919. serial No. 302,470. ...a

This invention and discovery, pertains Ato the engineering art and particularly relates to the art of constructing dams for impounding or diverting waters for the pur ose of conserving such waters and developlng hy- It is also applicable to bridges and other structures.

An object of this invention is to provide a practical dam by means of which it is made possible to safely dam any water channel. or chasm, as for instance, the chasm of the Colorado River within the Grand Canyon of the Colorado, and to extend such dam, with practical ease and perfect-safety, to any desirable height; say for example, 1200 feet more or less. Y

A dam for this purpose requires great strength and durability to preventfraotures which may be caused by vibrations or stresses; also to prevent destruction or 'damage from seismoticv action or other movements. f

, Another object is to avoid all danger of vibrations from overow without constructing a SeparatespiILWay.

Other objects are low cost and high speed of construction. f'

Another object is to prevent deterioration from the action lof the elements.v

Another object is to eliminate the necessity of raising scaffolding, forms or supports during construction.

This dam com rises a metal mono-plate face on a supporting element, such as a lilling, backing or core.l T nat is to say, I apply to a filling. backing or core of` concrete, or

some suitable substitute therefor, a plate which is inherently integral throu hout an entirepactive face of the dam. Said plate is practicable in the present state of the enginearing art if constructed of pieces manufactured at the mill. and welded together in situ at the dam.

It is important that said plate be so constructed and applied as to. answer all conditions of temperature and climatic changes.

An object is to take care of these requirements. l

A feature'of the invention resides in the peculiar construction of the. facing-plate with transverse grooves and ribs which serve, in a novel and improved manner, several use. ful purposes, amongst which may be mentioned superior strength of plate and of the backing conformed thereto; superior adhe` 'bination of face plates and filling, backing sion to the backing; adaptability to carry superimposed welght, as well as its own weight on the side walls or side footings inlstead of upon the base, which is thus relieved from gravity stresses that otherwise would be imposed upon it. This is especially true with the use of a concrete core because there is thus formed, by the plate and core, a composite unit having a greater strength and stiffness than would result from any other disposition of the same material for a like purpose.

Another advantage arisin from this transversely ribbed or groove construct-ion as applied to the down-stream face yof the dam, is the bathing and dissipating of any overl-low that may occur; a-n'd this obviates the necessity of `a water cushion at the foot v of the dam.

Another feature is the construction of the "mono-plate by means of oblique-arch ribs,

which are welded to curved bonding plates to form `therewith a single continuous unitary armor plate extending in complex arch form from wall to -wall of the channel and from bottom to top of the dam.

Another feature of the-f invention is the `construction of the dam upon the dprinciple of an abutment andarch combine so that the structure from wall to wall of the chasm or channel andfrom base to crest `of the dam 1s at every point held in position by top, bottom and lateral abutments so that no local movement can occur. Another feature resides 1n the novel comor core which results from the peculiar curves an'd shapes ofthe face plate or plates and the backing or core conformed thereto. This is especially marked inthe concrete construction where there -is mounted. on a f ace of the concrete core, and in combination therewith, an external armor plate hav ing arched corrugations that are embedded in channel-like seats in the face of the core, 100

and affording a confining reenforcement for the core, which reenforcement is bonded with y the core and is practically a unit therewith. In this connection, however, it is noted that by m turedyor pulverize'd core would be held in pol sition by the integral plates on the up-streamv side and the down-stream side, res ectively,

of the dam; so that it is practica to construct a" dam with a gravel, a sand or an 110 thai i novel construction of the dam, a fracheight is equal to two-thirds power of' the ordinate for that height (LO=NX23), maximum resistance is developed. By constructing the dam according to this formula the weight of the metal skin of the up-stream or down-stream face of the dam is so imposed upon the filling or coreas to hold the material of the core whether of clay, gravel,

broken stone or concrete in place by gravity and yet to resist the 11p-lifting force.of'any seepage water that might, perchance, percolate in through the core.

Said principle of contour construction is also applied to the horizontal section of the dam on both the up and down-stream faces thereof, except that the horizontal sectional contour at any level is composed of two spirals, the apexes of which unite at the middle of the dam. The base and ends of a dam of given volume and material constructed between spiral contours. in its vertical and horizontal sections, will have a larger surface in contact with the floor and walls of the chasm than is possible with former constructions. This greater contact area vgreatly increases the eiliciency of the dam as a water seal, andthe large adhesion and friction area thus provided, greatly increases the stability of the structure by forming an impervious barrier to prevent seepage of water thereunder to undermine the dama A'Ihe principle of construction in the preferred form of this'dam is that the principal and also the subordinate curves of the armor `;plate or plates are all concave externally and convex toward the filling, backing or core. In consequence of this novel construction, the eife'ct of both expansion of the break up and dissipate any wave or surge action caused superficiallv or otherwise, by wind or other forces. This is effected by the arch rib and concave plate construction svt torth in the foregoing and the following description.

'the nature of the views it is impossible to The invention not onlyl includes the structure as a whole, but also includes the specific parts constructed at the mill for this purpose; and includes the use of a specific construction of armor plate. In this connection it is -noted that in dams of considerable height or length the armor may be steel plates having a thickness of' about one inch, more or less, accordin to the requirements which will be well un erstood by engineers in view of this disclosure.

My improvement in the engineering art involves the discovery that a dam having an extreme coeiiicient of safety may be con# structed by manufacturing at a mill, pieces of metal adapted to form a face for the dam, and then welding such ieces .together in` situ on the face of the diam, thus forming the face of the dam-of an inherently integral piece. The invention also includesv the specific construction of the mill-pieces adapt-- ed to the construction of the dam as herein set forth. y

An object is to provide a construction that will invest the dam with an anchor system for securing the face plate and the core or backing positivelytogether and to distribute the load throughout the structure in such a manner that there will not be any accumulated load upon any footing or other local portion of the structure;

Other objects, advantages and vfeatures of invention'may appear from the accompany-` ing drawings, the subjoined detail description and the appended claims. I 100 The invention and discovery may be un- I derstood by reference to the accompanying drawings.

Figure 1 is a view adapted tov illustrate the proportions of the dam and the general lines of a vertical section of said dam taken mid-way between the side walls of the chasm across which the dam is built. The elevational, proportions shown in this view are those adapted to the construction of a dam no twelve hundred feet high, and two hundred feet at the base.l The lines on thel up-stream and down-stream faces of the dam are 1ntended to indicate the corrugations or ribs thereon, but it must be understood that from show the spacing, proportions, form or`construction of said ribs as they would be microscopic upon the scale of the figures. The plane of sight is slightly above the crest ofl the dam so that the level crest of the dam appears in this view to slope upward away from the middle section of the dam; 1t is. preferably level as seen in Fig. 9. p

Fig. 1 is a perspective fragmental view of the dam at the crest and indicates 1n a general way the outlines of the faces ofthe dam which it is impossible to show 1n Figs. l 2,-3.

,Fig 2 is a view analogous to Fig. 1 of a 180 Figs. 6, 7 and 8 are plan sections on lines indicated at as, m7, and ma respectively Fig..1.

Fig. 9 isa fragmental face elevation of the dam corresponding to that indicated in Figs. 1, 5, 6, 7 and 8. The parallel lines indicate the ribbed orcorrugated surface of the armor and are 'spaced apart in exaggerated proportions to avoid confusion of lines and the footings are indicated by dots at the ends of said lines. p

Fig. 10 is a ragi'ental vertical crosssection on a larger scale fthan the 4preceding views,.showing an upper part of an uncompleted mono-plate double-armored concretefilled dam in course of construction, a fragment of only one armor-plate being shown.

Fig. 11 is a transverse section of one of the rib-forming girder-beams 'detached and on a scale larger than that of Fig. 1Q.

Fig. 12is an isometric view of an' end of one of the beam-like mill-length sections adapted to the construction of the girderbeams at the dam.

Fig. 13 is a diagrammatic end plot o f the form of girder-beam mill length shown in Figs. 11 and 12'.'

Fig. 14 isa vertical section on line-, Fig. 15 of one of the ootings in situ ready to have a mill-length girder beam-like section welded thereonto for constructing one of the ribs. l

Fig. 15 is a View of the frontV face of one of the footings with stub in place.

Fig. 16 is an elevation, detached, of an anchoring splice bar, which is shown artly in solid and partly in dotted lines in Flg. 10. Fig. 17 is a cross-section on line ai, Fig. 16.

Fig. 18 is a fragmental elevation of that surface ofthe face plate which is next to the core of the dam.

Referring first to the construction having a concrete filling or coreias shown in'Figs.

1, 5, 6, 7, 8, 9 and 10, the metal armor face plate 1 may` be constructed of panelsk or strakes a, and ribs or girder-beams b made .up respectively of plate-like mill lengths or sections c acting asbon'ding-members and beam-like mill lengths or sections d, '(Figs. 10-13) integrally united in situ b any wellknown process of welding as by ame or by electricity.

In Figs. 10, 16, 17 and 18, splice bars e' of intersection.

are shown for use in uniting the ends of the l mill length plate sections. Said splice bars may or ma Y notbe constructed with anchor 'devices an in Fig. 17 a splice bar e having an anchor isshown in cross-section with the 70 ends of two plate-like mill lengths c in plan section, laid in the channels 3 of'said bar, ready for electrical or fiame welding to the splice bar.

I The anchors of the splice bars are shown 76 1n Figs 10, 16 and 17. The plate-like mill lengths c may be formed at the mill or place of manufacture to conform to its place in the completed structure. Preferably the core or backing 2, is faced on the up-stream so side and also upon the down-stream side by face-plates of the same character.- v

A sho'wn in Figs. 1, 2, 3, 5, 6, 7 and 8, these face-plates are constructed to a general contour respectively conforming, both ver- H5 'tically and horizontally, at any cross-sectional plane, to spirals projected in accordance with the formula (LO=NX2/3); in which the abscissa 'at any height from either base or from abutment to mid-plane is equal to J0 two-thirds powerofthe ordinate for that height hereinbefore stated, in which the length LO., of the ordinate of departure horlzo'ntall from the face of the dam is equal 4to t e two-third power' of ythedis- 95 tance H from the base of the dam to the intersection of the line with ordinate L.O. of

the curve.-

. -For illustration, in Fig. 1, assuming the height to be 1000 feet, LO is the Aordinate at the one thousand foot height, M is the terminal of the ordinate and N is the point M-N is equal to 10002/3 viz; 100 ft. At the five hundred foot ordinate LOQ is the terminal and R the point of intersection with the curve. Q-R. is equal to the two-'third power of 500; i. e.,. 5002/3. In Figs 5, 6, 7 and 8,- the bases B, ofthe horizontal spirals are at the points respectively, of the intersection of the spiral 1m with thevsupporting wall; andthe apex A,

is at the center of the structure. Inl Fig. 5 the length of thel central ordinate of 'departure LO is equal to the `two-third power of 525; the chasm being 1050 feet wide at the top or crest 18 of the dam. c

It is thus seen that the dam in the preferred form consists of a core -thicker at the base 19 or abutment 20 than at the crest 18 and also thicker at its abutments lateral 12o terminals 21 than at the thinnest middle or key22. e

In Fig. 10, the mill sections a of the plate are shown hatched in .one direction'and'the ribs b hatched in another direction to indicate the independence of such 'sections prior to their welding together at the joints f. Said mill sections of the plates are bent to predetermined curv'es2 both longitudinally and transversely to mainly conform to the tively, and said rib sections maybe con-v' structed at the mill to a novel cross section as shown in Fig. 11 for the double'purpose vof securing the greatest strength and stiliness for a (given amount of metal, and the greatest convenience for fitting and welding the plate sections thereto.

The rib or girder beam consists of a rolled steel membervwith an appropriate weight, which, for a dani of this size, will be, say, 210 pounds per running foot. The approf priate curved bonding plates a for the armor face plate of a dam of the size ind'icated in Figs. 1 and 5-9, may be'made of rolled steel one inch in thickness and 72 inches wide in the flat and curved as at 'g, to engage the entire curved surface, k, of the web and base of the beam d as indicated at f, Fig. 10. The construction and dimensions of the beams may vary with the size and duty of structures respectively for which they are made.

The arrangement of the ribs b and con cavities of the face plate on the downstream .fide of the dam operates to avoid all necessity of a separate spill-Way and of a water cushion. The upper face of each rib forms a baiile for the water flowing over the crest of the dam so that the fall of the water is broken at each rib line. Furthermore, the ribs overhang one another to form air spaces and channels 90 so that in addition to strengthening the down-stream face of the dam said ribs operate toward suction and `aeration of the water'. The concave surface of the plates, together with the overhanging ribs and action ofthe air superficial to the plates and below the ribs respectively, tend to give the impinging water a vortiginous motion causing the Water to commingle with the air and otherwise dissipate so that the force of its impact is minimized or greatly reduced.'

The face plates on both the up-stream side and the down-stream side are shown concaved; being in the form of a double arch.

The curved plates and ribs in combina-I ture stresses, whether from a rise or drop in temperature, will result, in either event, to cause the metal to press against the face of the core and not to separate from it. This tends to maintain the rigidity and strength of the dam under all possible conditions.

The splice bars e for use at the weld joints between the ends of the plates c are preferabl constructed of anchor form as detailed in lgs. 10, 16, 17 and 18. The web 4 and foot 5 of the anchor conform, substantially, to the web and base of the girder beam sections; bemg substantially of fish tail form in cross-section. v p

The head or outer rib of the anchor splice bar is constructedwith outer and lateral ribs 6, 7, 8, forming channels 9, in which the ed es 10 of the plate-like mill-sections c will e laid preparatory to Welding., The

welding of the plates to ribs and splice bars for any strake 1s eiected in the usual manner of electric or flame Welding before the concrete is poured at that height. The ancho r 5 termlnates short-of the ends of thev spllce bar to glve clearance at 11 for the bodies of the girder beams b.

The ribs or girders are supported in place by footings 12 shown in detail in Figs. 14 and 15, said footings comprising blocks of cast or forged steel, having concavities 13 at the back, and rib, or girderA-beam stubs 14 fixed in and projecting from the front. These footings are embedded in cement 15 in the channeled or otherwise prepared walls 16, of the chasm that is to be dammed, and the ribs or girder beams are attached thereto in any suitable manner as by welding,'

thus making the metal footing 12 and beam stub 14 integral with one another.

In practice, preparatory to final construction, the footings, the mill sections of ribs and plates and the necessary broken-rock or other aggregates and hydraulic cement are assembled at the dam site, and the bed and side Walls of the chasm or channel across which the structure is to be built is prepared to an appropriate contour for the reception of the foundation and side footings of the dam. The penstocks for an outlet omitted from the views for the convenience of the dratsman and to avoid confusion of lines, may then be placed in position immediately upon the foundation or at any height desired.

The construction of the dam proper may then be carried on as follows The up-stream and down-stream armor will be carried upward at least one strake above the core which is poured and tamped A in place between the plates so as to con- 'form to iand be in contact with the inner surface of the steel.

The steel work is carried up as follows: The footings are anchored to the inside of the canyon along a. predetermined contour., preferably to conform to the spiral mentioned above. The footings 12 respectively containing the stubs of the girder beams, are anchored rmly in place along the predetermined contour, and by welding the connecting rib mill sections d and the footing stubs of the beams together, they are made into continuous longitudinal members,pref.

erably rising toward the middle, but of the same general elevation at the wall terminals. The curved plates or bonding members c are then placed in position on the upper side of the girder b and together withthe s lice bars, e are welded into final position. pon the top edge of the plate panel thus formed, another course of beam sections thus formed is laid and welded -to the footing stubs and together, and to the supportlng bondlng plates and anchor splice bars; and 1n this way the construction is carried up one strake in advance of the filling or core, as statedabove. The steel members, previously having been formed to the specified curves, will make the arch design as shown in the drawof several times its weight. builtv betweeny parallel segments.

The weight of the steel armor is disposed so as to protect the base or toe from rupture by upward pressure or percolating Water.

In the instance shown inFig. 1 it may be assumed that the dam is either 1000 or 1200 feet in height, and that in the latter case it lhas had the contour of its vertical cross-secltion plotted with a unit of measurement equal to 12/10 of a foot so that there are 1000 units of measurement in the distance from base to crest of dam. The purpose of changing the length of the" unit of measurement according to the increased height is to avoid bringing the upper portion of a dam of great height into too close conformity to a vertical.

It is noted that by the application of the novel principles of construction herein set forth, the 'thinnest part of the dam is at the middle of the dam crest, and that such middle is the unitary crown of a double reverse arch. In any instance, however, before deflection could occur in the dam shown, both the concrete core and the con'cave armor plate on the'face receding from the pressure source would have to be sheared. In addition to this the webs of the splice bars would have to be sheared.

Another feature-of strength resides in the 'multiple arch construction developed by the arrangement of curved panels as set forth.

A further advantage arises from the concave face dam construction in that the hydrostatic pressure of the impounded water is radial to the concavity and consequently two-thirds, more or less, of the pressure is directed towards the walls and floor ofthe chasm. By reason of the double concave construction shown in Fig. 4 only the upper middle third works as an arch, and the extreme thirds at both ends and a measurable portion at the bottom work as abutments. 'Ihat is, the thrust of the pressure exerted on the portions of the dam adjacent each side and for a considerable distance across the chasm from each side, is on lines which will project into the side Walls of the chasm, consequently only the middle span of the dam is unsupported directly by said sidewalls. See Figs. 4 and 5. The portions supported by the sides may be considered abutments and the portion not so supported may be called the arch proper.

By reference to Figs. 5 and 6, it will be seen that the arch proper extends less than one-third the length of the dam, as indicated by the chord C, the arch resting on-the abutments D. i

The dam is thus composed of a combination of arch and abutments which affords greater strength for a given volume or mass of material than possible withformer constructions.

It is thus seen that the invention is a broad departure from former practice as to the va rious principles, parts and combinations of parts set forth, as well as in the completed structure, and that the invention may be applied 1n various forms within the judgment of the constructor; and that various features may be changed or omitted Without departure from the invention in other respects, and therefore, I do not limit the invelltionto the specific details, although it includes the same.

By providing a composite stress-resisting structure in which the portion for resisting compression is reenforced externally by opposite seamless facings; and more particularly, by one or more seamless externally concave steel facings, said facings working in tension, I confine the compression resisting element secure maximum strength, and ovoid oil likelihood of mooring, Shouoi-iog or weakening the reenforced portion of the structure by any force insuiiicient to rend the reenforcing portion.

I have also provided for maximized frictional and anti-seepage contact by introducing the inverted arch into dam construction, whereby such effect is maximized for a given mass.

It is also understood that though the central upper member of the dam is shown as a reverse arch, it may be differently constructed, and that I have only illustrated the invention in that form which I at present deem most desirable for the purpose of constructing a dam.

I claim.

1. A structural unit having a face, cross sectional contours of which, on planes approximatel at right angles to each other, substantial y conform, respectively, from abutment'to mid-plane and also from base to vcrest of such unit, to a formula in which the abscissa at any height is equal to the twothirds power of the ordinate for that height.

2. A structural un'it -having a corrugated face, cross sectional contours of which on planes approximately at right angles to each other from base to crest and from the abutments to middle plane between the abutments conform generally to a formula in which the abscissa at any height is equal to the two-thirds power of the ordinate for that` height.

3. A structural unit comprising a core and an inherently unitary middle face, contours of which face on cross sectional planes that are substantially at right angles to eachy other, substantlally conform respectively, from base to crest and from abutment to mid-plane to a formula in which the abscissa at any height from base toward crest or from abutment toward middle plane is equal to the two-thirds power of the ordinate.

4. A structural unit comprising a core .and an inherently unitary corrugated face, contours of which face on cross sectional planes that are substantially' at right angles to each other, substantially conform respectively from base toward crest and from abutment toward mid-plane, to a formula in which the abscissa at any height from the base or from abutment is equal to the two-thirds power of the ordinate for that height.

5 A'structural unit comprising a core and a transversely concave and horizontally corrugated and ribbed metal face, the corrugations beingy embedded in the core.

qi. A dam having up-stream and downstream faces that conform substantially, in vertical cross section, to a formula in which the abscissa at any height is equal to twothirds power of the ordinate for that height.

7. A dam having a transversely corrugated concave downstream face, the corrugations being overhanging ribs forming air-spaces beneath the ribs, respectively.

8. Adam comprisin a core and a transversely concave horizontally corrugated metal face backed by said core.

9. A dam comprising a double concave i11- tegral plate com osed of plate-like and girder-'beam-like e ements arranged to form a corrugated surface and back, and a backingv in which corrugations of said plate are embedded. i

10. A dam having its down-stream face aslant away from thev crest and corrugated with alternate ribs and concavities arranged transversely of thev channel which the dam spans, for the purpose of forming baiiles and air cushions to dissipate the falling water after it has passed over the crest and befor it reaches the foot of the dam.

11. A dam comprising footings, horizontal ribs integral with the footings and extending transversely there-between, from footingito footing, and plate-like members integral with the ribs and bridging the interrib spaces from footing to footing. i

l2. A dam comprising lateralV footin's, horizontally extending ribs integral'with t e footngs and extending transversely therebetween, from footing to footing, and horizontally bent plate-like members, integral with the ribs and brid ing the inter-rib spaces from footing to ootmg.

13. A dam' comprising lateral footings, ribs xed to said ,footings and sprun across from footing to footing,interrib p ate-like members bridging the nter-rib spaces, and a concrete body supporting the ribs and plate-like members.

. 14. A dam comprising lateral footings, ribsfixed to said footings and extending across from footing to footing, inter-rib plate-like members bridin the inter-rib spaces, and a concrete bo y acking `for the ribs and plate-like members.

15. A dam comprising lateral footings, ribs extending across from footing to footing in the form of an arch, inter-rib late like members integral with the ribs, an concave there-between, and a backing for the ribs and plate-like members. l

16. A dam comprising lateral footings, ribs extending across from footing to footing in the form of an arch, inter-rib latelike members integral with the ribs, an con-- cave there-between, and a concrete backing for the ribs and plate-like members.

' 17. A dam having laterally concaved upstream and down-stream faces comprising a" i core terminating in enlarged lateral abut-' ments and metallic face-plates lmade up of ribs and vertically concaved inter-rib platelike members incorporated with said core.

18. A dam comprising a concrete core and having laterally concaved up-stream and down-stream faces, terminating in enlarged lateral abutments, and metallic face-plates made up of ribs and vertically concaved inter-rib plate-like members incorporated with said core.

19. A dam com rising a plate composed of arched ribs an plate-like members integrally united; said plate-like members be ing longitudinally curved and arranged 'to form grooves on one side and corrugations on the other side of the plate; and a concrete backing in which the corrugations are embedded.

20. The method of constructing a dam across a chasm which comprises -anchoring to the inside of the chasm along a predetermined contour, up-stream and down-stream footings spaced apart and respectively containing stubs of girder beams; welding connecting rib mill sections and the lower footing stubs together to form girder beams spaced apart and having wall terminals at the footings; then placing curvedbonding members and splice bars and welding them together and to the girder beams to form 11p-stream and down-stream strakes spaced apart, repeating the operation and filling in a core between the lower strakes and continuing the placing, welding and filling operations and in this way carrying the construction upward with one up-stream and. one down-stream strake in' advance of the core, substantially as set forth.

21. A dam comprising a core and a faceplate extending beyond the margin of the core; said face-plate being provided with beam-like ribs; and metal footings with which the ribs are integral.

22. In a dam construction, a metal footing and a beam stub integral therewith and extending toward the middle of the dam.

23. A dam comprising a core terminating in enlarged lateral abutments and having external metallic reenforcements, the said reenforcements comprising outwardly projecting ribs and vertically concaved inter-rib plate-like members incorporated with said COI'e.

n 24. A dam comprising a core terminating in enlarged lateral abutments and havin externall metallic reenforcements, the sai reenforcements comprising a plurality of outwardly projecting ribs of the same size and vertically concave inter-rib plate-like mem.- bers incorporated with said core, the faces of said dam being curved from the top to the bottom thereof so that each of the projecting ribs Will intercept the water falling over the said dam.

25. A dam having laterally concaved upstream and down-stream faces, comprising a concrete core terminating in enlarged lateral abut-ments and metallic face-plates made up of outwardly projecting ribs and verticallyv concaved inter-rib plate-like members incorporated with said core.

26. A dam having a concave face and ribs projecting from such face and inclined upwardly toward the middle of such face.

27. A dam having a concave face and ribs projecting from such face and inclined and arched upwardly toward the middle of such face.

Witness my hand at Washington, D. C. this 5th day of June, 1919.

JAMES HENRY LEVERING. 

